EP1235949A1

EP1235949A1 - Method for applying a phosphate covering and use of metal parts thus phospated

Info

Publication number: EP1235949A1
Application number: EP01911738A
Authority: EP
Inventors: Hardy Wietzoreck; Klaus Bittner; Thomas Kolberg; Marion Wegner; Thomas Wendel
Original assignee: Schuellermann; Chemetall GmbH
Current assignee: Schuellermann; Chemetall GmbH
Priority date: 2000-03-07
Filing date: 2001-03-06
Publication date: 2002-09-04
Anticipated expiration: 2021-03-06
Also published as: KR100841156B1; AU4067901A; KR20020038581A; US7208053B2; CN1372602A; DE50111634D1; ATE348203T1; US20040231755A1; CN100334255C; AU778285B2; JP2003526012A; WO2001066826A1; CA2373145A1; DE10010355A1; EP1235949B1

Abstract

The invention relates to a method for applying a phosphate coating to metal surfaces by wetting with an aqueous, acidic phosphating solution, whereupon said phospating solution is dried, mainly without re-rinsing . The phosphate solution contains 26 -60 g/l zinc ions, 0.5 -40 g/l manganese ions and 50 -300 g/l phosphate ions, calculated as P2O5. The invention further relates to a method for applying phosphate coatings to metal surfaces by wetting with an aqueous, acidic phosphating solution, whereupon said phosphating solution is dried, mainly without re-rinsing, characterized in that the phosphating solution contains 10 -60 g/l zinc ions, 0.5 -40 g/l manganese ions, 50 - 300 g/l phosphate ions, calculated as P2O5, and 0.5 - 120 g/l peroxide ions, calculated as H2O2,and/or 0.5 - 50 g/l polymers, copolymers or/and cross polymers.

Description

Process for applying a phosphate coating and use of the metal parts thus phosphated

The invention relates to a method for applying phosphate coatings on metallic surfaces by wetting them with an aqueous phosphating solution and subsequent drying of the phosphating solution, and to the use of the metal parts coated according to the invention.

Phosphate coatings are widely used as corrosion protection layers, as a forming aid and as a primer for paints and other coatings. Especially if it is used as protection for a limited time, especially during storage and then e.g. are painted, they are referred to as a pre-treatment layer before painting. However, if there is no varnish layer and no other organic coating on the phosphate coating, treatment is used instead of pretreatment. These coatings are also referred to as conversion layers if at least one cation of the metallic surface, that is to say the surface of the metal part, is extracted and also used to build up the layer.

Among the coating processes, the so-called drying processes ("no-rinse processes") are of particular importance for the very fast coating of continuously running strips made of at least one metallic material. These strips can be sheets of small or very large width. A phosphate coating by wetting with a phosphating solution is usually applied to these strips directly after the galvanizing, but possibly also after suitable cleaning or degreasing and after rinsing with water or an aqueous medium and after activation of the metallic surface. Rinsing after the phosphate coating has dried could impair it, especially if the phosphate coating is not or only partially crystalline.

EP-A-0 796 356 describes a process for applying phosphate coatings to surfaces of zinc, iron, aluminum or their alloys by wetting them with a solution containing nickel, manganese and phosphate, which preferably also contains up to 4 g / l of zinc ions may contain, and by drying this solution.

EP-A-0 774 016 teaches a method for phosphating surfaces made of steel, zinc, aluminum or their alloys in each case by treatment with acidic zinc and phosphate phate-containing solutions and drying of the solutions without intermediate rinsing, in which the phosphating solution used has a zinc ion content of 2 to 25 g / l. H ₂ O ₂ with a content of only 20 to 100 ppm is recommended as an accelerator.

The disadvantage of the processes described in these two publications is that the phosphate layers produced in this way are predominantly amorphous and usually still contain free phosphoric acid and that, therefore, during subsequent wetting with an aqueous liquid, e.g. by splashing or condensation, an unintended reaction with the free phosphoric acid can occur and local impairments such as e.g. Discoloration, recrystallization and other changes in the predominantly amorphous phosphate layer can lead, which can interfere both visually and with respect to a subsequent process step. Such impairment as e.g. a dark streak can still be visible even after applying a varnish.

The object of the invention is to overcome this disadvantage of the prior art and, in particular, to propose a method for applying phosphate coatings on metallic surfaces in which the subsequent contact with an aqueous liquid or with moisture does not cause any damage and in which the phosphate layer formed at least the has the same quality as in the prior art.

The object is achieved with a method for applying phosphate coatings on metallic surfaces by wetting with an aqueous acidic phosphating solution and then drying the phosphating solution, usually without rinsing, which is characterized in that the phosphating solution - 26 to 60 g / l zinc ions,

- 0.5 to 40 g / l manganese ions and

- Contains 50 to 300 g / l phosphate ions, calculated as P ₂ O ₅ .

A high content of zinc ions promotes in particular the avoidance of a content of free phosphoric acid in the phosphate layer produced and also promotes the crystallinity of the phosphate layer. The content of zinc ions is preferably 28 to 50 g / l zinc ions, particularly preferably 30 to 48 g / l, very particularly preferably 32 to 46 g / l. In the following, the term metal parts encompasses metal strips in addition to parts such as metal strip sections and shaped and / or painted parts. This can mean, for example, first a metal strip and, in the subsequent process section after the strip has been cut, metal parts in the strict sense, first strip sections and then parts. Basically, a metal strip can first be pretreated and painted and then cut or first provided with a first pretreatment coating, then cut, then provided with a second pretreatment layer and then painted. There are also a number of other variants that are used less frequently.

A higher content of manganese ions has a positive effect on the quality of the phosphate coating, especially on the paint adhesion and on the corrosion resistance of the subsequently painted metal parts. The manganese ion content is preferably 2.5 to 30 g / l, particularly preferably 5 to 25 g / l and very particularly preferably 10 to 25 g / l.

The content of phosphate ions, calculated as P ₂ O _5, is preferably 58 to 280 g / l, very particularly preferably 60 to 260 g / l, in particular 72 to 240 g / l.

The object is further achieved with a method for applying phosphate coatings on metallic surfaces by wetting them with an aqueous, acidic phosphating solution and then drying the phosphating solution, usually without rinsing, in which the phosphating solution

- contains 10 to 60 g / l zinc ions or 0 to 60 g / l zinc ions on surfaces rich in zinc before wetting, - 0.5 to 40 g / l manganese ions,

- 50 to 300 g / l phosphate ions, calculated as P ₂ O ₅ , and

- 0.5 to 120 g / l peroxide ions, calculated as H ₂ O ₂ , or / and

- Contains 0.5 to 50 g / l of polymers, copolymers and / or cross-polymers.

The zinc ion content is preferably 18 to 56 g / l, particularly preferably 24 to 52 g / l, very particularly preferably 28 to 46 g / l.

The manganese ion content is preferably 12 to 30 g / l, particularly preferably 14 to 28 g / l, very particularly preferably 15 to 26 g / l. The Zn: Mn weight ratio can vary within wide limits. The content of phosphate ions, calculated as P ₂ O _5, is preferably 57 to 278 g / l, very particularly preferably 58 to 258 g / l, in particular 70 to 238 g / l. The content of peroxide ions is preferably 1 to 110 g / l, particularly preferably 2 to 100 g / l, very particularly preferably 5 to 85 g / l, in particular 10 to 75 g / l. 0.5 g / l H ₂ O ₂ corresponds to approximately 380 ppm.

The polymers, copolymers and / or crosspolymers are preferably those of the N-containing heterocycles, particularly preferably of the vinylpyrrolidones. The content of these polymers, copolymers and / or cross polymers in the phosphating solution is preferably 1 to 45 g / l, particularly preferably 1.5 to 42 g / l, very particularly preferably 2 to 40 g / l and even more preferably 2 , 5 to 36 g / l. 8.5 g / l in the phosphating solution give a proportion in the phosphate layer of approximately 51 mg / m ² .

Such polymers, copolymers and / or cross-polymers can be particularly helpful in phosphate layers which serve as pre-phosphating for forming in order to greatly reduce the so-called "powdering", namely the rubbing off of the phosphate layer during forming.

On the other hand, the addition of a polymeric alcohol can also be advantageous in order to use this alcohol to form phosphoric acid esters, particularly during drying, which have a beneficial effect on lubricants during shaping. At the same time, the addition of a polymeric alcohol can have an effect on the reaction with the excess free phosphoric acid which may be present in the phosphating solution in order to improve the crystallinity and the water resistance of the phosphate coating.

The phosphating solution can be free or essentially free of nickel or contain up to 20 g / l of nickel ions in the phosphating solution. The nickel content depends on the goal of the method according to the invention used. In a particularly preferred embodiment, no nickel is added to the phosphating solution; if a content of nickel ions should nevertheless occur in the phosphating solution, this content is usually due to the removal of nickel from the metallic surface of the metal parts to be phosphated as well as, for example, from pipelines and bath containers, which consist of a material containing nickel, or trace contamination of the raw materials Production of the phosphating solutions conditionally. The advantage of essentially nickel-free phosphating solutions lies in the complete or complete absence of a physiologically and environmentally questionable element.

Alternatively, however, a content of nickel ions can also occur in the phosphating solution, which can have an advantageous effect on the formation and quality of the phosphate coatings produced. Then the content of nickel ions is preferably 0.01 to 18 g / l in the phosphating solution, particularly preferably 0.03 to 15 g / l, very particularly preferably 0.05 to 12 g / l, even more preferably 0.1 up to 10 g / l, in the case of low zinc processes in particular 0.2 to 4 g / l or preferably 0.25 to 3 g / l.

The amount of the phosphating solution which is applied to the metal parts for drying can be in the range from 1 to 12 ml / m ² , preferably in the range from 1.5 to 10 ml / m ² , very particularly preferably in the range from 2 to 8 ml / m ² .

With the phosphating solution, a layer with a layer weight - determined on the deposited and dried phosphate layer - can be formed in the range from 0.2 to 5 g / m ² , preferably in the range from 0.3 to 4 g / m ² , very particularly preferably in the range from 0.4 to 3 g / m ² , even more preferably in the range from 0.5 to 2.5 g / m ² , in particular at 0.6 to 2 g / m ² .

The phosphating solution can be applied to the metal part by spraying, rolling, flooding and subsequent squeezing, spraying and subsequent squeezing, or by dipping and subsequent squeezing. The technique of application is known. In principle, any type of application of the phosphating solution is possible; however, the application variants mentioned are preferred. The squeezing serves to apply a defined volume of liquid per surface of the metal part and can also be replaced by alternative methods; rolling is particularly preferred e.g. with a "chemcoater" or a "roll coater".

The liquid film formed on the metal part with the phosphating solution can be dried on the surface of the metal part in the range from 20 and 120 ° C., in particular from 40 ° C., based on PMT temperatures, in particular at 50 to 100 ° C. Drying can take place, for example, by blowing hot air or by heating with infrared radiation, with the PMT method (PMT = peak metal temperature; determined by measuring the temperature of the surface of the metal part) can be regulated.

The phosphate layer formed in this way can have the following composition: it can be free or essentially free of nickel or have a content of up to 10% by weight of Ni and can additionally contain:

5 to 50% by weight of Zn,

- 1.5 to 14 wt .-% Mn and

20 to 70% by weight of phosphate, calculated as P ₂ O _5. It can contain in particular 0.1 to 3 or 0.2 to 2.5% by weight of Ni.

In particular, it can contain 10 to 45% by weight of Zn, preferably 12 to 42% by weight of Zn, particularly preferably 16 to 38% by weight of Zn.

It can contain in particular 3.5 to 13% by weight of Mn, preferably 4 to 12% by weight, particularly preferably 5 to 10% by weight, the layer quality generally improving with a higher manganese content.

It can preferably contain 25 to 60% by weight of phosphate, particularly preferably 28 to 50% by weight, very particularly preferably 30 to 40% by weight.

In a particularly advantageous process variant, the metal parts to be coated, preferably as metal strips, are first coated according to the invention with a first phosphating solution, and then they are added, preferably individually or by joining together, e.g. Adhesive or welding connected parts, after drying the first phosphating solution wetted with a second aqueous, acidic phosphating solution, this second solution - being free or essentially free of nickel or containing up to 20 g / l of nickel ions and

- 0 to 20 g / l zinc ions,

0 to 5 g / l manganese ions,

- 5 to 50 g / l phosphate ions, calculated as P ₂ O ₅

In most cases, the composition of the second phosphating solution corresponds to a basically known phosphating solution, and the method for applying it is also usually known, although this second solution is generally not dried. While the first phosphate layer is preferably in a band System is applied, the second phosphate layer can be applied, for example, in an automobile plant or at a device manufacturer.

The metal parts can be wetted with an activation solution or an activation suspension before wetting with the first and / or with the second phosphating solution. Such an activation provides the surface with crystal nuclei, which favors the subsequent phosphating and the formation of fine crystalline dense phosphate layers. An aqueous activation solution / suspension with a content of colloidally distributed titanium phosphate can advantageously be selected here.

The first phosphating solution can be obtained by coating with the phosphating solution e.g. with a roll coater or with a similar roller applicator on the metal part. The technique of application is generally known.

The first or / and second phosphating solution of the process according to the invention can advantageously contain ions of aluminum, boron, iron, hafnium, molybdenum, silicon, titanium, zirconium, fluoride and / or complex fluoride, at least one water-soluble alkaline earth compound, and / or organic complexing agents such as e.g. Contain citric acid. Fluoride can in particular be present in the range from 0.01 to 5 g / l in free or / and bound form, in particular in the range from 0.02 to 3 g / l, particularly preferably in the range from 0.05 to 2 g / l. In particular, the first phosphating solution can contain 0.0003 to 10 g / l, preferably 0.0004 to 5 g / l, particularly preferably 0.0005 to 0.05 g / l copper ions, the second a content of 0.1 to 50 mg / l copper ions, in particular in each case from 2 to 20 mg / l. The copper ions accelerate the formation of the phosphate layer and promote its quality.

The first or / and second phosphating solution of the process according to the invention is preferably free or essentially free of ions of lead, cadmium, chromium, chloride and / or cyanide, since these substances are not sufficiently environmentally compatible or / and impair the phosphating process and the quality of the phosphate layer can belittle.

The first and / or the second phosphating solution can in particular be set so that the ratio of the sum of the cations to phosphate ions, calculated as P ₂ O _{5, is} in the range from 1: 1 to 1: 8. This ratio is preferably in the range from 1: 1, 2 to 1: 7 and particularly preferably in the range from 1: 1, 5 to 1: 5 advantageous in many cases to work with a proportion of free phosphoric acid in the phosphating solution so that a reaction with the metallic surface can take place; this releases metal ions from the metallic surface, which in turn react with the unbound phosphate ions to form insoluble phosphate.

In the first or / and second phosphating solution, the S value as the ratio of the free acid to the total content of the phosphate ions can be in the range from 0.03 and 0.7. This S value range then corresponds approximately to the pH value range from 4 to 1. The pH value is preferably in the range from 3 to 1.5 and very particularly preferably in the range from 2.8 to 1.7 , For the second phosphating solution, the S value is preferably 0.2 to 0.03.

To determine the free acid, 1 ml of the phosphating solution is diluted to approx. 50 ml with distilled water, possibly with the addition of K ₃ (Co (CN) ₆ ) or K ₄ (Fe (CN) ₆ ) for the purpose of elimination disruptive metal cations, titrated with dimethyl yellow as an indicator with 0.1 M NaOH until the color changes from pink to yellow. The amount of 0.1 M NaOH consumed in ml gives the value of the free acid (FS) in points. The total content of phosphate ions is determined by titrating the titration solution after adding 20 ml of 30% neutral potassium oxalate solution against phenolphthalein as an indicator until it changes from colorless to red with 0.1 M NaOH , The consumption of 0.1 M NaOH in ml between the envelope with dimethyl yellow and the envelope with phenolphthalein corresponds to the total acid according to Fischer (GSF). If this value is multiplied by 0.71, the total content of phosphate ions is obtained (see W. Rausch: "The phosphating of metals". Eugen G. Leuze-Verlag 1988, pp. 300 ff).

The so-called S-value is obtained by dividing the free acid value by the total acid value according to Fischer.

The total acid (GS) is the sum of the divalent cations contained and free and bound phosphoric acids (the latter are phosphates). It is determined by the consumption of 0.1 molar sodium hydroxide solution using the phenolphthalein indicator. This consumption in ml corresponds to the total acid score. The first and / or the second phosphating solution can contain at least one accelerator. Basically all accelerators can be used. The phosphating solution preferably contains an accelerator such as a peroxide, a substance based on nitroguanidine or based on hydroxylamine, a chlorate, a nitrate, a perborate and / or an organic nitro compound such as paranitrotoluenesulfonic acid. A content of H ₂ O ₂ is particularly preferred here, since a residue-free acceleration is possible with this, since only water and oxygen remain. The first and / or the second phosphating solution can advantageously contain a peroxide additive, preferably H ₂ O ₂ , in a concentration in the range from 1 to 100 g / l, preferably from 5 to 90 g / l, in particular from 10 to 80 g / l, calculated as H ₂ O ₂ . Above all, due to the high content of H ₂ O ₂ , at the usually high speeds in the belt system, it is possible to accelerate all chemical reactions occurring in the wet film and during drying within a few seconds and to effect a corresponding through-reaction. This has a very advantageous effect on the layer quality, particularly in the case of these high zinc processes.

Advantageously, at least one compound based on formic acid, succinic acid, maleic acid, malonic acid, lactic acid, perboric acid, tartaric acid, citric acid and / or a chemically related hydroxycarboxylic acid can be added in order to stabilize the bath or the concentrate or the supplementary solution, in particular in order to avoid or reduce precipitations from one of these solutions and to increase the crystallinity of the phosphate layer, as a result of which the water resistance of the phosphate layer is significantly improved. The total addition of such compounds to such a solution can range from 0.01 to 5 g / l. The content of at least one of these compounds is preferably in the range from 0.1 to 3 g / l. This has a content of sodium perborate of 0.2 to 3.5 g / l, tartaric acid in the range of 0.2 to 0.8 g / l or citric acid in the range of 0.12 to 0.5 g / l especially proven. Even better results were achieved with a combination of 0.2 to 0.8 g / l of sodium perborate and 0.2 to 0.8 g / l tartaric acid.

The first or / and second phosphating solution can be applied at a temperature in the range from 10 to 80 ° C. The first phosphating solution is preferably operated at room temperature or at a slightly higher temperature; only in special cases are the metal parts and / or possibly also the phosphate Rung solution heated to a slightly elevated temperature, for example, to accelerate the drying of the applied solution.

The first phosphating layer can remain unchanged when wetted with the second phosphating solution or slightly dissolved in the upper area and its structure changed and / or easily removed by the second phosphating solution, while an additional phosphate layer can be deposited from the second phosphating solution. but does not have to be separated. However, it has been shown that the resistance of the first phosphate layer to liquids such as e.g. Splashing water or cleaning liquid, in particular the alkali resistance, the higher, the more crystalline the layer is.

The second phosphating solution can include be applied to the metal part by spraying, flooding or dipping. The technique of application is generally known. Any type of application of the phosphating solution is possible; however, the application variants mentioned are preferred.

It may be advantageous to apply a passivation solution directly to the first or second phosphate layer, in particular by spraying, dipping or rolling. Here, a rinse solution is preferably used to further increase the corrosion resistance and paint adhesion, the self-containing at least one substance based on Cr, Ti, Zr, Ce or / and other rare earth elements including lanthanum or yttrium, tannin, silane / siloxane, phosphorus -assembling molecules, phosphonates or polymers can contain.

The first or / and second phosphate layer dried on the metal part can be wetted with an oil, a dispersion or a suspension, in particular with a forming oil or anti-corrosion oil and / or a lubricant such as a dry lubricant, for example with a wax-containing mixture. The oil or the lubricant serves as additional temporary corrosion protection and can also facilitate a forming process, whereby the deformed metal part also has increased corrosion resistance. A coating with an oil can also be of interest on the second phosphate layer if the metal parts to be painted are to be transported to a painting plant further away. After pre-phosphating, oil is preferably applied first before the metallic substrate is deformed. An existing oil layer or lubricant layer can be removed from or from the first or second phosphate layer in order to prepare the coating for painting, forming, assembly, gluing or welding. The oil must be removed for subsequent painting, while it can be removed in other processes.

The metal parts provided with a first or / and second phosphate layer can be coated with a lacquer, with a different organic coating or / and with an adhesive layer and, if necessary, formed before or after such a coating, the metal parts coated in this way also before painting or organic coatings can also be glued or / and welded together with other metal parts. Forming, gluing or welding can also take place in the presence of an oil. The oil is often removed with the cleaner before the second phosphating begins. The metal parts provided with a first or / and second phosphate layer can be provided with an organic or lacquer coating either before or only after the shaping or / and assembly. A wide variety of organic coatings are known today or can be used on a phosphate layer. Not all organic coatings fall under the definition of paints.

The metal strips coated with phosphate according to the invention can be oiled in a so-called belt system and, if necessary, degreased and / or cleaned before they are subsequently coated in a painting system. For economic reasons, de-oiling before gluing or welding is preferably avoided.

The phosphate-coated metal parts according to the invention can be used for the production e.g. Oiled of equipment cladding if necessary, cut and shaped if necessary or degreased or / and cleaned if necessary before they are then coated in a paint shop, if desired. However, they can also be cut and reshaped when painted.

The metal parts according to the invention which are coated with phosphate can be oiled and shaped for the production of, for example, automobiles, several metal parts then being welded together, glued together or otherwise connected and then The assembled metal parts can be degreased and / or cleaned before they can then be coated in a paint shop.

The metal parts coated according to the invention can be used as pre-phosphated metal parts for a further conversion treatment or for a new conversion pretreatment - in particular before painting - or as pretreated metal parts - especially for the automotive industry - especially before painting or as end-phosphated metal parts, which may still be subsequently varnished, otherwise coated organically, coated with an adhesive layer, formed, assembled and / or welded. They can be used for the manufacture of components or body parts or pre-assembled elements in the automotive or aerospace industry, in the construction industry, in the furniture industry, for the manufacture of devices and systems, in particular household appliances, measuring devices, control devices, test equipment, construction elements, claddings and Small parts can be used.

The processes according to the invention are outstandingly suitable for a large number of metallic surfaces, in particular for surfaces of steel, iron, aluminum, magnesium, zinc and their alloys in each case, preferably for galvanized or alloy-galvanized surfaces, and provide particularly high paint adhesion and high-quality corrosion protection.

With the methods according to the invention it is possible to use a completely nickel-free phosphating process for high phosphate layer qualities, for example as a pretreatment before painting.

It has been shown that the more crystalline it is, the less sensitive the aqueous phosphate layer is to aqueous liquids, moisture and other adverse, especially corrosive media. The phosphate layer according to the invention has also proven to be extremely insensitive due to its crystallinity. The crystallinity has surprisingly developed particularly well at higher and high zinc contents in conjunction with a high peroxide content. Even better crystallinity of the phosphate layer and thus an even better water resistance and resistance of this layer to, for example, alkaline cleaners has resulted if an additional activation is carried out before the phosphating. In most cases, the phosphating systems in the automotive industry are equipped with weakly alkaline cleaners, but in some cases also with strongly alkaline cleaners. It was surprising that the first crystalline pre-phosphating layer according to the invention is significantly more resistant to the influence of strong alkaline cleaners. During the short treatment times usually used with a strong alkaline cleaner, the first phosphate layer according to the invention was not or only slightly impaired.

A mix of different materials such as Metal parts made of an uncoated steel and pre-phosphated metal parts can easily be coated side by side using a method according to the invention.

In the case of pre-assembled or assembled metal parts, pre-phosphating in cavities can achieve better corrosion protection than in the cited prior art, even without the application of a lacquer.

Examples

The subject matter of the invention is explained in more detail below on the basis of exemplary embodiments.

Test series A:

Metal sheets made of electrolytically and, in parallel, hot-dip galvanized steel strip were treated as follows: Sheet dimensions: 105 x 190 x 0.7 mm.

First there was a spray cleaning in an alkaline detergent bath, followed by a short rinse with water three times. After the rinsing process, the metal sheets were prepared for the application of the phosphating solution according to the invention by immersing them in an activation solution containing titanium phosphate and then squeezing off the liquid film. The phosphating solution was applied using a roll coater. After the application of the phosphating solution, the sheets were dried in an oven at 180 ° C. for 30 seconds (PMT = 80 ° C.). The resulting layer weight of the dried liquid film was 1.5 g / m ² . The treatment sequence is briefly outlined below:

Cleaning: Spray with Gardoclean® 338, 8 g / l, 60 ° C, 10 sec Rinse: With cold water, 10 sec diving

Rinse: spray with cold water, 4 sec

Rinse: With deionized water (= VEW), 5 seconds of immersion

Activate: With Gardolene® V6513, 4 g / l in VEW, 5 sec immersion Squeeze: Using a squeeze roller

Rolling: Phosphating solution according to the invention (see table

1) Drying with a roll coater: In the oven at 180 ° C, 30 sec, PMT = 80 ° C.

Table 1: Composition and density of the phosphating solutions according to the invention in g / l or g / cm ³

Table 2: Layer composition in mg / m ² on electrolytically galvanized steel strip (EG)

The layer weight of the pre-phosphating layer was 1.2 to 1.8 g / m ² ; the zinc content varied with the acid value and ranged from 62 to 820 mg / m ² .

Surprisingly, there was a clear tendency towards better crystallinity of the phosphate layers with an increasing cation content of the ratio cations: P ₂ O ₅ . With an improved crystallinity, these layers are also more resistant to water, liquid cleaning compositions and other liquids, so that, for example, water splashes which get onto the intermediate pre-phosphated tapes or tape sections do not lead to stains and other markings which are blatant Cases can remain visible through the subsequently applied post-phosphating and / or through subsequent lacquer layers.

In a series of tests, the pre-phosphated test panels were painted immediately afterwards either with only a cathodic automotive dip coating or with an overall automotive paint system and gave the usual automotive paint tests, e.g. Cross-cut testing after wet storage, VDA climate change test etc. also with nickel-free coatings the same good results as with the test panels, which were phosphated twice according to the invention and then painted.

It was also surprising that these sample sheets coated according to the invention - even if they were used free of nickel - gave equally good results in comparison with conventional trication-automotive phosphating with a NiMn-modified low-zinc phosphating, since excellent results with the latter phosphating so far have only been achieved with one certain nickel content was reached.

The pre-phosphated sheets made of electrolytically galvanized (EG) or hot-dip galvanized steel (HDG) and hot-dip galvanized steel with a coating based on ZnFe (Galvaneal ^® ) were subjected to various forming tests. For this purpose, a forming oil of approximately 0.5 g / m ² typically used in the automotive industry was applied to all pre-phosphated and non-pre-phosphated (VB 28) test panels.

Table 3: Results of the forming tests on pre-phosphated test sheets made of differently coated steel

With the Fiat The Multifrottement Test, the coefficient of friction is determined and indicated after 1 and after 10 moves. The smaller the coefficient of friction, the better the results. This reflects the properties of the pre-phosphating layer that make it easier to slide.

The maximum blankholder force test determines the force in kN that is required to achieve the only necessary flow of the material of the sheet with lateral clamping with a stamp acting from above, which creates a cup-shaped depression, without the sheet thereby tears. The higher the applied forces without cracks, the better the results.

The Weight Loss Cup test determines the weight loss during forming, whereby both the pre-phosphating layer and the Galvaneal ^® coating can be removed. A hold-down force of 10 kN, an indentation diameter of 50 mm and a punch diameter of 90 mm were used, whereby the punch was not pushed through the pre-phosphated sheet and no cracks are generated. The weight of the test parts before and after the forming was determined and the weight loss in g / m ² , which should be as small as possible, was specified.

The aim of these investigations was to be at least in the same order of magnitude of formability with the prephosphating agents according to the invention as with comparable nickel-containing prephosphating agents. The values of the nickel-free samples with a Galvaneal ^® layer are significantly better than those of the nickel-containing samples with a Galvaneal ^® layer and significantly better than those of the non-pre-phosphated samples.

Test series B, C and D: The test series B and C were carried out on electrolytically galvanized steel strips or steel sheets and the test series D on aluminum alloys for the automotive industry. The following compositions of the phosphating baths were used for the pre- and post-phosphating.

Table 4: Compositions of the phosphating solutions 1 to 5 with contents in g / l:

* unless otherwise stated in the individual experiment

In the test series B (B 35 and VB 35), part of the electrolytically galvanized steel strip was pre-phosphated with the phosphating solution 1 after treatment with a titanium-containing activation solution in a separate bath using the no rinse process on a roll coater. Here, a layer weight of almost exactly 1.5 g / m ^{2 of} the pre-phosphating layer was achieved. The pre-phosphating layer had excellent crystallinity and resistance to water and other liquids, so that no staining, for example due to splash water that wets the phosphate layer, absorbs soluble components and then dries up, cannot occur.

Thereafter, the pre-phosphated (B 35) or non-pre-phosphated strips (VB 35) were cut and the sheets obtained were treated with an activation solution containing titanium and then phosphated with the phosphating solution 4. The non-pre-phosphated sheets showed a layer weight of the post-phosphating layer of about 3.0 g / m ² , while the pre-phosphated sheets had a layer weight of only about 2.3 g / m ² . Because of the good crystallinity and durability, the pre-phosphating layer surprisingly only led to the formation of a thinner, but essentially similarly high-quality post-phosphating layer, the layer thickness of the post-phosphating layer being sufficient and even chemicals being saved.

Subsequently, a KTL coating of a BASF paint was first applied in an automobile production line and then a filler and top coat with a paint system in accordance with VW Mosel was applied. The investigations carried out on these painted sheets led to the following results.

Table 5: Results of the corrosion protection and paint adhesion tests in test series B (* condensation water constant climate test over 240 h according to DIN 50017 KK):

Here values of the infiltration up to U 2.5 mm, the paint flaking up to 10% and the cross-hatch grading up to Gt 2 can be regarded as sufficiently good. The sheets pre-phosphated and post-phosphated according to the invention essentially achieved the same high quality as the sheets not pre-phosphated and only post-phosphated. In addition, two assembly groups were manufactured, one of which only had pre-phosphate and lacquer layers and the other had only post-phosphate and lacquer layers; the only pre-phosphated painted assembly group gave at least equivalent corrosion and paint adhesion results as the only post-phosphated painted assembly group. It was thus possible to show that the sheets which had been pre-phosphated and, if necessary, subsequently additionally phosphated and painted according to the invention fully take into account the conditions of the automotive industry. It is therefore also possible to rephosphate and varnish component assemblies in which only a few, but not all, of the parts that are connected to one another have been prephosphated.

In test series C, all sample tapes (B 36 - B 43, VB 36) except for a sample tape (VB 37) were pre-phosphated according to the invention on a roll coater using the no-rinse process. VB 37, on the other hand, was pre-phosphated in the conventional spraying process: With the low cation contents as chosen for VB 37, it would not be possible to produce sufficiently thick coatings with the short wetting times of the no rinse process. The sample tapes were treated with an activation solution containing titanium before pre-phosphating at B 40 and VB 37. For the pre-phosphating, the phosphating solution 1 was used for B 36 to B 41 and the phosphating solution 2 was used for B 42 and B 43 without or with different levels of peroxide. All of the metal sheets were then reactivated with the activation based on titanium, which had already been used in some cases, and treated with the after-phosphating solution 5 in order to form a second phosphating layer.

Table 6: Conditions and results of the pre-phosphating or post-phosphating in the test series C.

Vorphos- average layer weight in phatie grain g / m ² each only of pillar size in a phosphate layer μm layer

Quality of the pre-phosphating layer: A amorphous, not waterproof B partially crystalline, almost waterproof, very crystalline and waterproof, resistant to liquids.

It was found that the crystallinity of the pre-phosphating layer with a high zinc content depends essentially on the sufficient content of peroxide in the phosphating solution. In this series of experiments, it was found that the layer weight of the pre-phosphating layer increased more if it was previously treated with an activating solution, and that a slightly lower layer weight of the post-phosphating layer was then formed than otherwise.

The sheets coated in this way were coated in an automobile production line with lead-containing KTL paint PPG 742-962 / G5, but not with other paint layers. Corrosion resistance and paint adhesion were determined on these sheets.

Table 7: Results of the corrosion and paint adhesion tests for test series C:

Here values of the infiltration up to U 2.5 mm and the cross-hatch grading up to Gt 2 can be regarded as sufficiently good.

While the crystallinity and durability of the pre-phosphating layer showed an optimum H ₂ O ₂ content of around 40 to 70 g / l, slightly better results of paint adhesion were shown for 80 g / l. Overall, the no-rinse examples according to the invention proved to be at least equivalent to the conventional spray pre-phosphating process of VB 37.

In test series D, sheets made of aluminum AA 5754 or AA 6016 were pre-phosphated in a no-rinse process with phosphating solution 1, but without the addition of H ₂ O ₂ . The layer weights were varied systematically, and part of the metal sheets were oiled. Thereafter, forming tests were carried out: It was found that the cold forming of the sheets, which had been pre-phosphated and not oiled, still had a certain amount of friction which corresponded to the friction which occurred at Deformation of sheets resulted which had been coated with a Zr-containing pickling system, as is used as the standard quality, and then coated with oil. However, significantly better forming results were obtained with pre-phosphated and oiled sheets. At the same time, the strength of an adhesive connection was tested: the strength of the bonded pre-phosphated sheets was of a comparable order of magnitude to that of the pickled sheets.

The pre-phosphated or pickled sheets were subsequently phosphated with phosphating solution 4, but with 18.2 g / l P ₂ O ₅ , with 0.23 g / l free fluoride and with almost the same acid values as given in Table 4, then rinsed with a rinsing solution based on zirconium fluoride and coated with a cathodic dip. The pre-phosphated sheets showed no worse corrosion and paint adhesion result than the initially pickled sheets, which represent a standard quality. At the same time, other such sheets were additionally provided with a filler and topcoat for an overall automotive paint system and tested in parallel. In all cases, coating was carried out with and without oil or with a dry lubricant based on acrylate that is commercially available for the automotive industry and specially optimized for this purpose, and additionally with oil before - if necessary after heat treatment for 30 minutes at 205 ° C, as is the case in the automotive sector is partly common - was post-phosphated and painted in all cases. All pre-phosphated variants showed the same good or, in exceptional cases, a slightly better result than the initially pickled sheets (Table 8).

Table 8: Test results of the pre- and post-phosphated and coated sheets of series D made of aluminum alloys AA 6016 in comparison to initially pickled and then phosphated and coated sheets.

Claims

claims

1. A method for applying phosphate coatings on metallic surfaces by wetting with an aqueous acid phosphating solution and then drying the phosphating solution, mostly without rinsing, characterized in that the phosphating solution

- 26 to 60 g / l zinc ions,

- 0.5 to 40 g / l manganese ions and

- Contains 50 to 300 g / l phosphate ions, calculated as PA.

2. A method for applying phosphate coatings on metallic surfaces by wetting with an aqueous acid phosphating solution and then drying the phosphating solution, usually without rinsing, characterized in that the phosphating solution

Contains 10 to 60 g / l zinc ions or, in the case of zinc-rich surfaces, 0 to 60 g / l zinc ions before wetting,

- 0.5 to 40 g / l manganese ions,

- 50 to 300 g / l phosphate ions, calculated as P ₂ O ₅

- 0.5 to 120 g / l peroxide ions, calculated as H ₂ O ₂ , or / and

- Contains 0.5 to 50 g / l of polymers, copolymers and / or cross-polymers.

3. The method according to any one of the preceding claims, characterized in that the phosphating solution is free or essentially free of nickel or contains up to 20 g / l of nickel ions.

4. The method according to any one of the preceding claims, characterized in that the phosphating solution contains polymers, copolymers and / or cross-polymers, in particular of N-containing heterocycles, preferably of vinylpyrrolidones.

5. The method according to any one of the preceding claims, characterized in that a phosphating solution is used in which the ratio of the sum of the

Cations to the phosphate ions, calculated as P ₂ O ₅ ^m i range from 1: 1 to 1:. 8

6. The method according to any one of the preceding claims, characterized in that an amount of the phosphating solution in the range of 1 to 12 ml / m ^{2 is} applied to the metal parts for drying.

7. The method according to any one of the preceding claims, characterized in that a layer with a layer weight of the deposited and dried phosphate layer in the range of 0.2 to 5 g / m ^{2 is} formed with the phosphating solution.

8. The method according to any one of the preceding claims, characterized in that the phosphating solution is applied by spraying, by rolling, by flooding and subsequent squeezing, by spraying and subsequent squeezing or by dipping and subsequent squeezing on the metal part.

9. The method according to any one of the preceding claims, characterized in that the liquid film formed with the phosphating solution on the metal part is dried on the surface of the metal part at temperatures in the range from 20 and 120 ° C in relation to PMT temperatures.

10. The method according to any one of the preceding claims, characterized in that a phosphate layer is formed with the following composition:

free or essentially free of nickel or up to a content of 10% by weight of Ni, 5 to 40% by weight of Zn,

- 1.5 to 14 wt .-% Mn and

- 20 to 70% by weight of phosphate, calculated as P ₂ O ₅

1 1. The method according to any one of the preceding claims, characterized in that the metal parts after drying a first phosphating solution according to at least one of the preceding claims are wetted with a second aqueous, acidic phosphating solution, said second solution being free or substantially free of nickel or contains up to 20 g / l nickel ions in the phosphating solution and - 0 to 20 g / l zinc ions,

0 to 5 g / l manganese ions and

5 to 50 g / l phosphate ions, calculated as P ₂ O ₅

12. The method according to any one of the preceding claims, characterized in that the metal parts are wetted with an activation solution or activation suspension before wetting with the first or / and second phosphating solution.

13. The method according to any one of the preceding claims, characterized in that the first phosphating solution contains at least 0.3 mg / l copper ions or the optionally used second phosphating solution 0.1 to 50 mg / l copper ions.

14. The method according to any one of the preceding claims, characterized in that a first or / and second phosphating solution is used, in which the S value as the ratio of the free acid to the total content of the phosphate ions is in the range of 0.03 and 0.6.

15. The method according to any one of the preceding claims, characterized in that the first and / or second phosphating solution at least one accelerator such as a peroxide, a substance based on nitroguanidine, based on nitrobenzenesulfonic acid or based on hydroxylamine, a chlorate, a nitrate Perborate or an organic nitro compound such as Contains paranitrotoluenesulfonic acid.

16. The method according to any one of the preceding claims, characterized in that the first and / or second phosphating solution contains a peroxide additive, preferably H ₂ O ₂ , in a concentration in the range from 1 to 100 g / l, calculated as H ₂ O. _2nd

17. The method according to any one of the preceding claims, characterized in that the first or / and second phosphating solution contains at least one compound based on perboric acid, lactic acid, tartaric acid, citric acid and / or a chemically related hydroxycarboxylic acid.

18. The method according to any one of the preceding claims, characterized in that the first or / and second phosphating solution contains ions of aluminum, boron, iron, hafnium, molybdenum, silicon, titanium, zirconium, fluoride and / or complex fluoride, in particular 0 , 01 to 5 g / l fluoride in free or / and bound form, contains.

19. The method according to any one of the preceding claims, characterized in that the first or / and second phosphating solution is applied at a temperature in the range of 10 to 80 ° C.

20. The method according to any one of the preceding claims, characterized in that a passivation solution is applied directly to a phosphate layer, in particular by spraying, dipping or rolling.

21. The method according to any one of the preceding claims, characterized in that the dried on the metal part first or / and second phosphate layer with an oil, a dispersion or a suspension, in particular a forming oil or anti-corrosion oil and / or a lubricant, is wetted.

22. The method according to any one of the preceding claims, characterized in that an existing oil layer or lubricant layer is removed from or from the first or second phosphate layer.

23. The method according to any one of the preceding claims, characterized in that the metal parts provided with a first or / and second phosphate layer are coated with a lacquer, with a different organic coating or / and with an adhesive layer and, if necessary, formed, the coated in this way Metal parts can also be glued together, welded together and / or otherwise connected with other metal parts.

24. The method according to any one of the preceding claims, characterized in that the metal parts provided with a first or / and second applied phosphate layer are coated either before or only after the shaping or / and assembly with a coating according to claim 23.

25. Use of the metal parts coated by the process according to at least one of claims 1 to 24 as pre-phosphated metal parts for a further conversion treatment or for a new conversion pretreatment, in particular before painting or as pretreated metal parts, in particular for the automotive industry, especially before painting or as end-phosphated Metal parts that may be subsequently painted, otherwise coated organically, coated with an adhesive layer, formed, assembled and / or welded together.

6. Use of the metal parts coated by the method according to at least one of claims 1 to 24 for the production of components or body parts or preassembled elements in the automotive or aerospace industry, in the construction industry, in the furniture industry, for the production of devices and systems , in particular household appliances, measuring devices, control devices, test devices, construction elements, cladding and small parts.